Last season, Greenbriar Jam Kitchen received 500 pounds of donated beach plums to make 1,000 jars of jelly, which sold — and quickly sold out — at $14 a jar. “That $14,000 was essentially the jam kitchen’s budget for the year,” Ray Hebert, trustee chairman at the Cape Cod Museum of Natural History, said.
This may be one of Cape Cod’s most unusual fundraisers.
To keep Sandwich’s 117-year-old Greenbriar Jam Kitchen operating, officials are asking supporters to plant a beach plum hedge in their yards this fall and donate the fruit when it shows up next year.
“We don’t need you to write a check; you can support the jam kitchen with donated fruit,” Ray Hebert, trustee chairman at the Cape Cod Museum of Natural History, said. The museum includes the Thornton Burgess Society in Sandwich, which is believed to be the oldest continuously operating jam kitchen in the country.
Greenbriar accepts other donated fruit, but for Cape Cod, beach plum jelly is the iconic sweet spot.
Looking a bit like cranberries but in a variety of hues from blue-purple to yellow, beach plums are a fruit that grows wild in the sandy soil of the windswept Eastern coast. Those lucky enough to come across a patch of the rare gems while hiking keep the location secret, and even those who grow a cultivated strain at home do so quietly so as not to tempt plum poachers.
“When they bring in the beach plums, they don’t even tell me the location,” Hebert said.
Last season, Greenbriar Jam Kitchen got 500 pounds of donated beach plums to make 1,000 jars of jelly, which sold — and quickly sold out — at $14 a jar. “That $14,000 was essentially the jam kitchen’s budget for the year,” Hebert said.
In addition to supporting Greenbriar, a beach plum hedge could help your yard and the Cape’s environment.
“People always ask me ‘What can I do?’ There is good scientific evidence for the importance of native trees, shrubs and wildflowers,” Chris Neill, Ph.D., climate scientist at Woods Hole Research Center, said in an interview about a Native Plants Study released in the spring.
A wide variety of yards in six cities, including Boston, were studied. One of the key findings was that native plants (such as beach plums for the Cape) drew bees for pollination, triggering a chain reaction toward an ecosystem that is specifically local.
“The fact these things are native makes a real difference in attracting insects and feeding birds,” Neill said.
Incorporating native plants also cuts down on the size of manicured lawns, he said, which is important on Cape Cod because lawn fertilizers are associated with nitrogen runoff that pollutes water.
Russell Norton, agriculture and horticulture extension educator for the Cape Cod Cooperative Extension program, emailed that beach plums are “a suitable edible native that can easily be incorporated into a home landscape or in a natural border.”
He said the extension service encourages the plant’s use by making seedlings available at the annual native plant sale.
Hebert planted beach plums in the backyard of his Brewster home and has watched the phenomenon at work. He has helped Mother Nature along bycreating a wood pile so carpenter bees can nest.
Hebert bought his beach plum plants from Crocker Nurseries in Brewster, where 2-to-3-foot plants sell for $36-$45.
Nursery stock buyer David Shea said he brought in 25 beach plum plants this year “and they were gone within a week.” He attributed the popularity to a general increase in food gardening by people at home for quarantine and by the fact that beach plums are one of the few food plants that are native (blueberries are the other) and therefore are permitted to be planted near conservation areas.
Crocker Nurseries sold the basic strain of beach plum with blue-purple fruit. When Hebert found yellow beach plums growing in the wild, he sent a sample to Cornell University, where Roger Ort, from the Cornell University cooperative extension service, named the naturally occurring variation after Hebert and planted clippings in upstate New York.
Ort documents unusual species of fruit he and his wife use to make and sell jams and jellies.
“Beach plums were a big deal back in the day,” Ort said. “Areas like Cape Cod had beach plum clubs selecting the best varieties, organizing hikes to look for beach plums and documenting, naming, what they found.”
Hebert said he wasn’t looking to have a beach plum named after himself, but rather just to satisfy his curiosity about the yellow variety.
He had some yellow-red plums but mostly the dark blue-purple variety this week at Greenbriar Jam Kitchen, where Hebert worked alone watching eight pots over cast-iron gas burners.
Greenbriar is closed because of COVID-19 concerns but normally a dozen people would be in the old-fashioned kitchen learning to make jam or jelly, using a stick-to-the-back-of-the-spoon test to judge viscosity.
“When we have classes, we teach the old-fashioned, homespun way,” Hebert said. “But when I’m making jelly to sell, it’s a science.”
Instead of the back of a spoon, Hebert, a professional candy maker, uses a hydrometer to measure the ratio of liquid-to-solid (BRIX score) of the juice and sugar in the final step of jelly making.
There are many things to think about: the fruit’s size is a factor as is the surface area of skin, since the natural pectin that thickens jelly is found in the skin.
The beach plums, usually slightly bigger than berries, are washed and thrown in, twigs and all, with a small amount of water. Fruit is boiled twice to extract all the juice, which is refrigerated until Hebert is ready to add sugar, cook once more and jar the product.
In the lobby next to the kitchen, guests are stopping in to buy beach plum and other kinds of jelly. Outside the kitchen window, workers are removing sumac and rosa rugosa (beach roses used in rose hip jelly) in preparation to plant beach plums.
“They make a beautiful hedgerow because the blossoms are quite gorgeous,” Hebert said. “If you’re going to have a hedge, why not plant something native?”
Find Gwenn Friss on Twitter: @dailyrecipeCCT